1. Field of the Invention
The present invention relates to automated lawn mowers, and more particularly pertains to a new and improved automated lawn mower which utilizes obstacle sensors and touch grass sensors to control the direction of movement of a lawn mower through a computer interfaced feedback control of independent wheel drive motors. The conventional forms of automated lawn mowers heretofore devised require the setting of a boundary track or indicator around the plot of land to be mowed. Alternatively, the conventional forms of automated lawn mowers require a detailed precise programmed map of the plot of land to be mowed to enable the mower to follow a proper mowing course. In order to overcome the disadvantages of providing a programmed lawn plot map or constructing a boundary track indicator, the present invention provides an automated self propelled lawn mower which utilizes infrared obstacle detectors in conjunction with cut or uncut grass sensors to provide feedback control to independent wheel drive motors for steering the mower on a proper course.
2. Description of the Prior Art
Various types of automated lawn mowers are known in the prior art. A typical example of such an automated lawn mower is to be found in U.S. Pat. No. 3,550,714, which issued to S. Bellinger on Dec. 29, 1970. This patent discloses an automated self propelled mower which operates on the principle of random motion within a boundary. The boundary is established by a signal carried on a conductor which must be installed around the periphery of the plot of land to be mowed. The mower includes a sensor for receiving the boundary signal as the mower approaches the boundary and control circuitry for steering the mower away from the boundary. U.S. Pat. No. 3,570,227, which issued to S. Bellinger on Mar. 16, 1971, discloses a self propelled lawn mower for cutting grass in a random and unattended manner. The mower is propelled by a battery and comprises a frame supported on a pair of front castor wheels and a pair of rear drive wheels. The drive wheels are coupled to a continuously rotating drive shaft by individual clutch brake mechanisms. When a boundary wire installed around the perimeter of the plot of land to be mowed is sensed by coils on the frame, the drive wheel farthest away from the boundary is unclutched and braked to pivot or turn the mower. U.S. Pat. No. 3,650,097, which issued to C. Nokes on Mar. 21, 1972, discloses a self propelled lawn mower for movement over a given land area in a preplanned route. The mower has a frame and a steering mechanism with a tape extending between two reels with intermediate elements contacted sequentially by the tape for providing a programmed tape mechanical control of the course of the mower. U.S. Pat. No. 3,924,389, which issued to S. Kita on Dec. 9, 1975, discloses a lawn mower which utilizes a sensor mounted on the front of the mower to detect the edge of the swath by sensing the difference in height between uncut and cut grass in the swath. An electrical signal is produced by the sensors when it contacts the uncut grass and passes therethrough a minute electrical current. The current is amplified by a solid state amplifier circuit and fed to a pair of clutch brake assemblies for steering the mower along the edge of the swath. These clutch brake assemblies are connected for selectively braking and or driving the wheels of the mower. A sensor and control circuit design is disclosed for guiding the mower along the swath edge with a minimum of hunting even with grass is damp or growing sparsely. U.S. Pat. No. 4,184,559, which issued to H. Rass on Jan. 22, 1980, discloses a lawn mower with a mechanical sensor and piloting mechanisms which enable it to pilot itself along the edge line between the grass already cut and grass not yet cut, in a fairly straight course, and then to reverse its direction at the end of a run, move itself sideways, towards the uncut grass and proceed with another run. The lawn mower drive wheels are driven by a planetary gear mechanism which is coupled both to the motor and to rotatable sensor brushes mounted ahead of the drive wheels so that the planetary mechanism transmits power to the drive wheels only when the sensor brushes encounter resistance, such as from uncut grass, ahead of the drive wheels. The planetary gear mechanism is mounted on a guide frame that is pivotally mounted to the drive wheel frame so as to engage a first of two counter rotating gears linked on the wheel frame to the drive wheels. Forward impact against the guide frame causes it to pivotally rock so as to engage the second of the counter rotating gears to reverse direction of travel of the lawn mower. U.S. Pat. No. 4,347,908, which issued to R. Anderson on Sept. 7, 1982, discloses a self propelled lawn mower which is caused to traverse a plot of land to be mowed by following a line arranged over the land in a predetermined manner. A mechanical follower mechanism is provided on the lawn mower for following the course line. U.S. Pat. No. 4,528,804, which issued to T. Williams on Jul. 16, 1985, discloses a sensing unit for a row crop harvester guidance system which comprises a rotatably mounted crop engaging arm biased into a crop engaging position by a torsion spring. The spring tension is adjustable to vary the amount of force required to actuate the crop engaging arm. Variation of the force is desirable to permit the sensing unit to operate reliably in a variety of crop and field conditions. U.S. Pat. No. 4,603,753, which issued to S. Yoshimura et al on Aug. 5, 1986, discloses an automated lawn mower which utilizes a pair of spaced photo sensors for detecting the swath boundary between cut and uncut grass. Control circuitry actuated by these photo sensors operate electro-magnetic valves which operate hydraulic cylinders for steering the front and rear wheels of the mower.
While the above mentioned devices are suited for their intended usage, none of these devices provide an automated self propelled lawn mower which utilizes independent feedback controlled drive motors for independently driving the drive wheels of the lawn mower in accordance with information provided by touch grass sensors and infrared obstacles sensors. Inasmuch as the art is relatively crowded with respect to these various types of automated lawn mowers, it can be appreciated that there is a continuing need for and interest in improvements to such automated lawn mowers, and in this respect, the present invention addresses this need and interest.